This invention relates to improved plastic containers having enhanced strength characteristics and optimum sealing of its internal contents. The containers herein disclosed may be molded through economical molding techniques and used as containers for paint, motor oil or other liquids and material in a wide range of sizes from less than a quart to larger containers of more than five gallons. Superior sealing and strength characteristics are attained by the designs of the invention through novel retention of the lid and/or through use of a plurality of reinforcing ribs formed either in the container mouth or in the lid, or in both the container and the lid for a combined effect.
In recent years, plastic containers are being increasingly used for a wide range of liquids and chemicals which traditionally were filled in metal cans and the like. Some of the important objectives in plastic container designs have been to insure that the structure equals or exceeds the ability of the metal can to prevent leakage, resist forces, and maintain retention of the lid under encountered conditions. Many prior plastic containers have failed to satisfy these and other objectives because of inadequate strength of the mouth portion of the container and of the lid. Such unsatisfactory designs are unable to maintain dimensional rigidity as required for optimum sealing and resistance to hoop and radial stresses. For example, it is desirable that the mouth of the container maintains a circular configuration to aid in sealing of the lid and to insure that the container may be filled by conventional high speed filling machines, an important objective.